The UPS three cameras all support dual power input and can support dual power input from different sources. It seems that solutions from different sources are better than solutions from the same source because two power sources can be redundantly backed up. However, in fact, the dual power input solution from different sources is not the best. This article provides specific analysis for several situations.

The original design concept of UPS was to use the same input power source for the main circuit (rectifier) and bypass. When the mains power supply fails, the UPS will switch to battery working mode. When there is an internal fault or output overload in the UPS, it switches to the bypass load. When the fault is restored or the overload is eliminated, the UPS automatically switches back to normal working mode. This is the logic of normal UPS operation.

If different sources of dual power input are used, the working logic is that when the main and bypass sources are different, the output voltage and phase of the UPS always track the bypass. This is specified in the UPS design. When the main power supply fails, the UPS switches to battery working mode instead of switching to bypass power supply. When the battery pack is exhausted, the UPS switches to bypass power supply. Although the bypass power supply is used to supply power to the load, the load is not protected by the UPS. Various interferences in the power grid, such as lightning surges, voltage fluctuations, electrical noise, etc., can pose a threat to the load at any time, which goes against the purpose of setting up the UPS. In addition, in the case of dual power supply, the battery backup time is generally short because the probability of problems occurring in both power sources is very small. Therefore, when the battery is quickly depleted, the load will receive unimproved power, which poses a high risk. Therefore, the solution of UPS dual power input with different sources is not the best.